Point-of-care testing for coagulation studies in a stroke protocol: a time-saving innovation

Study Objectives

Time counts in thrombolytic therapy for stroke. An international normalized ratio (INR) greater than 1.7 may preclude its use. We studied whether the use of point-of-care testing (POCT) for INR in the emergency department (ED) may substitute for the same test done in the central hospital laboratory, thereby reducing time to treatment.

Methods

We performed a prospective observational study comparing a POCT analysis of INR (i-STAT-1; Abbott Inc, Abbott Park, Ill) with a simultaneously drawn sample sent to the central laboratory. We tested a convenience sample of adult patients taking warfarin who presented to the ED of a tertiary teaching hospital.

Results

Thirty-two patients were enrolled. A receiver operator curve analysis was performed. Sensitivity and specificity were calculated for laboratory INR cutoff of 1.7. The area under the curve was 0.979 (95% confidence interval [CI], 0.843-0.991). When POCT INR was 2.1, the sensitivity for laboratory INR being higher than 1.7 was 100% (CI, 62.9%-100.0%), and the specificity was 90.5 (CI, 69.6-98.5). When POCT INR was 1.8, the specificity for laboratory INR being lower than 1.7 was 100% (CI, 83.7%-100%), and the sensitivity was 62.5% (CI, 24.7%-91.0%). The regression coefficient (r) value was 0.9648.

Conclusion

Correlation of POCT INR with that of the central laboratory and receiver operator curve characteristics are excellent. In general, POCT INR is about 0.3 higher than the laboratory INR. This is not generally of clinical importance, but when using cutoff of 1.7 (central laboratory), it may be. We describe a 3-tiered system for use of POCT INR in determining use of tissue-type plasminogen activator.